The present invention relates to the construction industry, and more specifically to the formation of a pre-engineered grate or covered multi-walled trench including an assembly for forming the trench and a frame for the assembly. The need for a multiple walled containment trench with frames has evolved with the need to prevent seepage of objectional materials through the trench walls and into the surrounding ground.
The need for this invention has resulted from Federal Regulations, particularly from the E.P.A. For instance, underground tanks used for fuel or other chemicals must have a tank inside a tank. Should a leak occur in the inner holding tank, the fluid would be captured by the outer tank feeding to a low point leak sensor or feeding to a strip sensor along the bottom of the outer tank (such as one made by Rachem Corp.), setting off an alarm that leakage had occurred. It is expected that similar regulations may be forthcoming for trenches containing certain liquids. Therefore, the need exists for multi-walled trenches which allow for leak detection.
The general concept of trench drainage systems has long been used. Trenches are used where liquid run-offs occur, such as in chemical plants, food processing operations, pulp and paper mills, pharmaceutical manufacturing, bottling plants, in parking garages and parking areas of shopping centers. The fluid from a trench generally goes into a catch basin or sewer large enough to release the material from the trench as it arrives. The top of the trench is normally covered with a slotted grate to allow entrance of the fluids, catching of debris, load carrying capacity for whatever may pass over it, and is made of a material that will withstand the corrosiveness of the fluid entering the trench. In some applications, the top of the trench may be solidly covered, such as crossing sidewalks or where conduits are carried within the trench and fluid entry is minimal and not necessarily desirable.
Minimal development has been done in the field of double containment trenches with frames to support grates and covers. In the prior art, a double walled polymer concrete channel has been made. These channels were constructed in relatively short lengths, requiring many joints where leaks could occur. Another problem existed in that heavy traffic would also frequently pass over the trenches. In the prior art, proper protection of the inner and outer trench, or liner, was not provided. Thus, failure of the trench or liner could easily occur, causing leakage.
Another disadvantage in the prior art exists in the lack of provisions for replacement of the frame, the inner trench liner, or other trench liners without having to essentially remove the old system and install a new one at an extremely high expense. Furthermore, the inner and outer walls of these containment trenches were attached to each other, thus allowing no independent contraction or expansion of either wall, resulting in buckling and failure of the containment system.
In the prior art, either trenches have no slope or a fixed slope. Thus, the engineer cannot design the trench to his requirements but must use what comes "off the shelf", thus limiting his options. Also, limited widths and depths of trenches have been offered. Therefore, the fluid flow was restricted to the available trenches, instead of trenches being designed for the fluid flow.
Therefore, there exists a need for a multi-containment trench system which will provide a minimum number of joints to reduce possible leakage points.
There exists a need for a multi-containment trench system that can accommodate a variety of temperatures over a wide range without rupturing the walls or breaking the joints apart from either heat, cold, expansion or contraction.
There also exists a need for a multi-containment system that offers an extra protection against leaks at the joints of the trench.
There exists a need for a multi-containment system that offers protection to the inner and outer walls or liners from heavy traffic passing across the trench.
There exists a need for long length trenches with virtually no joints.
Further, there exists a need for a cost effective method of replacing the frame, the trench liner or liners should a leak occur or the liner begins to wear out.